A recording/reproducing apparatus comprising a digital modulator circuit (18) which receives digital signals that are to be recorded, means (17) for controlling a laser beam that is guided from a laser source (10) to an optical disk (1) depending upon the output of said digital modulator circuit (18), first optical means (9, 8, 7, 6, 4) which guide the laser beam from said laser source (10) to said optical disc (1), second optical means (4, 6, 11, 14, 15) which guide the laser beam returning from said optical disk to an optical detector (16), an actuator (5) which is served with a servo error signal obtained from said optical detector (16) and which adjusts the laser beam for said optical disk, a low-pass filter (19) which is served with the output of said digital modulator circuit, and removing means (20, 21) that remove low-pass component output signal that has passed through said low-pass filter (19) from said servo error signal. In recording the data, low-pass components are extracted from the digitally modulated output to adjust the gain and, thereby to cancel the low-pass components contained in the servo-error signal. Namely, digitally modulated low-pass components are removed from both the tracking and focussing servo error signals, making it possible to stably apply a servo signal. In reproducing the data, the power of laser beam is smaller than in recording the data, and the low-pass components in the recorded signals are not so intense as to adversely affect the servo signal. Therefore, the modulation system has a mild gain making it possible to highly densely record the data.